A Brief Discussion on Research Hotspots and Key Technologies of Automotive Bus

The research and development of automotive bus systems can be divided into three stages: the first stage focuses on the basic control systems of vehicles (also known as comfort bus systems), such as lighting, electric windows, and central locking. The second stage studies the main control systems of vehicles (also known as power bus systems), such as electronic injection ECU control systems, ABS systems, automatic transmissions, etc. The third stage examines the integration, real-time control, and information feedback among various electronic control systems in vehicles. According to the development plan for automotive electronic technology in our country, after entering the 21st century, automotive electronic technology can reach the level of foreign cars in the 1990s. To shorten the gap with foreign automotive technology and enhance competitiveness, relying solely on technology introduction is not conducive to development. The independent research and development of automotive bus and network application systems is on the rise. Currently, research and application of automotive buses in our country are still in the initial stage, and the application trend of automotive buses is evident. Now is a good time to engage in this research. The focus of research on automotive buses is on the fact that the models in our country are mainly European and American models, which primarily use the CAN bus. Therefore, almost all domestic models using bus technology currently employ the CAN bus. Thus, the research and development of automotive buses should be chosen in conjunction with the actual situation both domestically and internationally. The CAN bus complies with the ISO/OSI reference model but only specifies the protocols for the physical layer and data link layer; the application layer protocols need to be defined by the user. Many chips support the CAN low-level protocol, including on-chip MCUs and off-chip CAN controllers. There are also many application layer protocols developed by users. For example, the DEVICNET protocol defined by AB is an application layer protocol based on the CAN protocol. The SDS bus launched by Honeywell also defines its own application layer based on CAN. It can be seen that the focus of research on automotive CAN buses is to develop ECU hardware and application layer software for specific models and to form an onboard network. The key technology utilizes the CAN bus to construct the onboard network. The key technical issues that need to be addressed include: 1) technical issues such as the rate, capacity, priority, and node capacity of bus transmission information; 2) reliable data transmission in high electromagnetic interference environments; 3) determining large transmission delay times; 4) network fault tolerance technology; 5) network monitoring and fault diagnosis functions. Overview of the bus network system: With the improvement of the performance of automotive electronic control systems, especially the performance of controller chips and software, the improvement of automotive bus network systems not only allows for information sharing and harness savings but also provides richer software functions, enhancing product value and competitiveness, and meeting the demands for automotive reliability and comfort. The bus technologies corresponding to these functions include: network management: controllers monitor the network operating status through network management, and once a communication fault is detected, immediate fault handling is performed. The sleep and wake-up functions of network management can coordinate the power management of each controller, thereby reducing battery consumption when the vehicle is parked. Diagnostics: Diagnostics can not only read fault codes but also implement two important functions: offline configuration and detection, as well as program downloading. The automatic offline configuration and detection function can quickly and comprehensively configure and detect the functions of the controller (such as window zero position configuration and anti-pinch detection) to ensure the quality of the vehicle and speed up the production line. Through the program downloading function, automotive manufacturers can refresh the software of the controller at 4S stores, thereby reducing the recall costs caused by software defects. Measurement and calibration: During the development of new models, the rapid control prototype controllers using measurement and calibration technology can conveniently adjust control parameters and algorithms in real-time through computer and network systems, significantly reducing development cycles and costs. This technology is widely used in the development of new energy vehicles in Europe, the United States, and Japan. Foreign manufacturers such as General Motors, Ford, Volkswagen, and domestic manufacturers such as FAW, Dongfeng, SAIC, Changan, GAC, and Chery have integrated bus technology into a universal network platform for high, medium, and low models. In this way, variations in the network system are reduced, software reuse is increased, and development costs are lowered. The network platform of vehicle manufacturers consists of network standards, testing specifications, and protocol stacks (network-related embedded software). The commercial vehicle network platform complies with the SAEJ1939 standard; the passenger vehicle network platform has its own characteristics for original equipment manufacturers, but more and more original equipment manufacturers are adopting international standards to share supplier resources. Meanwhile, an increasing number of suppliers are choosing to have protocol stacks developed by specialized companies, thereby reducing development manpower and cycles. The development process of the bus network system: The construction of the network platform and the development of the network system adopt the V-model development process, as shown in the figure below. The V-model defines a clear and effective development process: OEMs complete the formulation of system requirements and component requirements from system requirements to component requirements and release the component requirements to suppliers; after suppliers complete component development, OEMs complete the integration and verification of multiple rounds of prototype vehicles and prototypes from component testing to system testing.